Every day, hundreds of asteroids fall towards Earth. Small asteroids cause no harm, but large asteroids can have major consequences. There is no doubt that a killer asteroid will one day cross paths with the Earth… and that we will need to be ready to act. Knowing this threat is coming, the world's space agencies have set up specialist departments for detecting and exploring asteroids. For the first time in history, they are even planning on changing an asteroid’s orbit to protect the planet. Will we be able to avoid global catastrophe?